Alfa not working

OpenGL OpenGL: Basic Coding
1

I’m trying to use the alfa test to draw
a polygon with a hole in it. The hole has
an alfa value of 0 and the rest of the texture has 255. I use the GEQUAL function with a value of 128 but nothing happens…

What is the problem? Is there a special way I have to init my framebuffer to get alfa tests to work? or is it something else?

Thanks
Harry

2

Called glEnable(GL_ALPHA_TEST)?

And if you are using glAlphaTest() you must pass the alpha reference as a float in the range [0,1].

3

Well the problem is that I’m enabling alfa test but nothing happens(I use 0.0 -> 1.0 values also). I can’t explain it. My video
card is based on nVidia’s TNT2 and supports
it for sure. The problem is somewhere else

4

I’m not sure if this will affect the alpha test at all, but it can be that you have to use a framebuffer that support alpha - RGBA. Maybe you are using a RGB framebuffer.